Orthogonal Frequency-Division Multiple Access (OFDMA) is a multi-user version of the popular orthogonal frequency-division multiplexing (OFDM) digital modulation scheme. Multiple access is achieved in OFDMA by assigning subsets of subcarriers to individual users. OFDMA divides the radio spectrum into time-frequency Resource Units (RUs). A coordinating entity such as an Access Point (AP) assigns RUs to associated stations or equipment for reception or transmission.
802.11ax is a type of wireless local area network (WLAN) in the IEEE 802.11 family of WLANs. IEEE 802.11ax is designed to operate in existing spectrums assigned to WLANs. Unlike legacy WLANs (e.g. 802.11ac and prior) which use OFDM to allocate an entire frequency spectrum to a client station or equipment during each time slice (i.e., time division), 802.11ax uses OFDMA. OFDMA allocates different parts of the frequency spectrum to different users during each time slice. An AP implementing 802.11ax uses a scheduler to assign different time-frequency divisions (i.e., RUs) to different client stations or equipment.